Bridge infill and first solid layer have the same alignment (Version 2.7.4+win64)

[juckendesAuge]

Description of the bug

“Solid Infill” goes in the same direction as “Bridge Infill”. Wouldn't diagonal be more suitable so that the first “solid infill” layer that belongs to the 4 “top layers” already looks better and is therefore probably also more stable?

diagonal Skadis_for_prusa_MK3S.zip

Project file & How to reproduce

Unzip the .zip.
Open the 3mf File.
slice it and check Bridge infill at Layer 3.80
and Solid infill at Layer 4.20

Prusa Slicer Version 2.7.4+win64

For information only:
I have added “M310 S0” to the Start G-Code under Printer Settings at the very end, as I always get a thermal anomaly warning with 0.6 and 0.8mm nozzles. With 0.4mm nozzles and 0.25mm nozzles it works fine. I have also run through the complete thermal calibration with a 0.8mm nozzle. Unfortunately, this does not bring any improvement.

Checklist of files included above

• Project file
• Screenshot

Version of PrusaSlicer

Prusa Slicer Version 2.7.4+win64

Operating system

Windows 10 64Bit

Printer model

Prusa MK3s+ Firmware: e3d_REVO_fw_MK3S+_3_13_3_7094

[u89djt]

From a fellow user tracking what goes on in here with a workaround and some amateur observations:
That's really interesting. In your specific case, you can make it lay the bridge infill at 90 degrees to the solid infill by changing the "fill angle" setting to 135 degrees as a workaround. You can also rotate the object by a tiny bit and the bridge infill will flip. Maybe these changes affect where the slicer starts searching for a good direction, I don't know. If you scale your object down to 99%, the bridging and solid infills run at 90 degrees to each other, so it seems like just bad luck rather than a bug. You got good bridging and you got good infill, but the constraints on the two processes are very different, so they won't necessarily reach similar conclusions about where they should go. I suppose the slicer would have to propose multiple solutions for the bridging layer to then come back and choose between when the layer above has been built. Imagine the mayhem if there's more than one region of bridging infill.

I wondered if the mesh might have caused issues because it has some strange features, but rebuilding a clean brep body of it didn't make any difference. Here's that in case it's any use to you too:
rebuilt body.zip

[juckendesAuge]

Thank you @u89djt ,

my concern is that Prusa Slicer automatically offsets the bridge infill by 90° to the solid infill. If the previous setting is better for bridging, then at least the orientation of the solid infill should be adjusted.

Edit:
I was aware that you can change the bridge angle manually. However, I only noticed that the bridge infill and the first solid infill have the same orientation when I was printing. So it's already printed.

[Tupson444]

I noticed this issue recently too, although I'm still using 2.7.3.

It might have been some "bad luck" in slicing, but it was a rather simple shape (basically rectangular at the bridging infill layer), so it is more probably a bug (it shouldn't be difficult to avoid aligning the next layer when the bridging infill is all in the same direction).